Generally, an ultrasonic probe has an array vibration element (vibration element group) composed of a plurality of vibration elements. The ultrasonic probe outputs ultrasonic beams from the vibration element group to perform electronic scanning. Examples of the electronic scanning type include an electronic linear scanning and an electronic sector scanning.
High-voltage transmission driving signals are supplied to the vibration element group, which causes ultrasound to be transmitted to each of the vibration elements. The ultrasound transmitted from each of the vibration elements is combined to form an ultrasonic beam. A power loss in an electro-acoustic conversion in the vibration element group is output as heat. In other words, the vibration element group generates heat, which then is conducted to each part of the ultrasonic probe. This heat conduction also increases a surface temperature of an acoustic lens. Since the ultrasonic probe comes into direct contact with a living body; it is very important to manage the temperature of the vibration element group or the ultrasonic probe in terms of safety for protecting a living body from burns and the like (there are statutes, safety standards, etc., for the temperature management of the ultrasonic probe).
Here, in the electronic linear scanning, a temperature distribution in the vibration element group along the arrangement direction of the elements is considered. For example, in a color flow mapping mode in which a two-dimensional color flow image (color doppler mode image) is overlaid and displayed on a two-dimensional monochrome tomographic image (B-mode image), for example, the transmission should be performed once for the B-mode and ten times for the color doppler mode per one beam address (the transmission condition varies depending on modes). Moreover, in many cases, a vibration element region where a color doppler mode image is formed is set at a part of the vibration element group. In this case, temperatures at respective locations in the vibration element group are not the same, i.e., the temperature at an area where the transmission for the color doppler mode and the transmission for the B-mode are performed together is increased further. Therefore, if the temperature of the vibration element group is assumed to be uniform without considering a mode or a region where an ultrasonic image is formed, the temperature will be misunderstood locally.
Among conventional ultrasonic diagnostic apparatuses, as a first ultrasonic diagnostic apparatus, there is one that performs temperature management by monitoring a voltage and a current of a commonly-used transmission power source, i.e., monitoring the total amount of electric power related to the transmission.
Further, as a second ultrasonic diagnostic apparatus, a type is proposed (for example, see Patent Document 1) in which the temperature is obtained by a software calculation considering transmission conditions.
Further, as a third ultrasonic diagnostic apparatus, a type is proposed (for example, see Patent Document 2) in which a plurality of transmission power detection circuits are arranged at positions corresponding to the vibration element group so as to obtain temperature based on the detection results. FIG. 5 is a block diagram showing a partial configuration of the third ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus includes a plurality of vibration elements 1 (vibration element group 11) that transmit and receive ultrasound, a plurality of transmission circuits 2 (transmission circuit group 12) that input transmission driving signals to the vibration elements 1, a transmission pulse generation unit 4 that supplies transmission pulses to the transmission circuits 2, and a transmission power source 3 that supplies electric power to the transmission circuits 2. The ultrasonic diagnostic apparatus further includes electric power detection units 40 that detect the amount of electric power from transmission driving signals of the respective transmission circuits 2, and a transmission monitoring unit 23 that detects the temperature of the ultrasonic probe from outputs of the electric power detection units 40.